1. Field of the Invention
The present invention relates to an inkjet printing apparatus that forms images on a recording media by discharging ink droplets on the recording media.
2. Discussion of the Related Art
Conventionally, inkjet printers form images by discharging ink droplets from a recording head while intermittently moving a recording medium as the recording head is displaced in a main scanning direction which is orthogonal to the feeding direction, or auxiliary scanning direction, of the recording medium.
In a conventional inkjet printer, an image forming process is interrupted when an ink tank runs out of ink. The interruption may lead to a decline in the efficiency and accuracy of the image forming process. Japanese Laid-Open Patent Application H08-216426 and Japanese Laid-Open Patent Application 2002-29041 describe inkjet printers that are provided with a plurality of ink tanks for storing ink and monitoring the remaining amount of ink in each tank, such that, in order to continuously form images, the printer switches to a second ink tank as the ink in a first ink tank falls below a predetermined amount.
The conventional printer comprises a sensor for detecting the remaining amount of ink in each of the plurality of ink tanks. This, however, leads to a problem of a more complicated inkjet printer configuration, which causes lower manufacturing and maintenance efficiencies and higher manufacturing and maintenance costs. Specifically, the aforementioned deficiencies are prevalent in inkjet printers that form images on recording media with a size greater than A0, which require a greater amount of ink consumption and concurrently a greater number of ink tanks.
For ink tanks storing anaerobic ink, such as ink that deteriorates upon contact with specific gases, photophobic ink, such as ink that deteriorates upon contact with specific lights, and color ink, a method of detecting the ink level inside the ink tank, a method of detecting the weight of the ink tank, and a method of detecting ink tank deformation via flexible ink tanks are among the methods used for detecting the remaining amount of ink in ink tanks. However, the methods described above entail a problem in that, the detection accuracy of the remaining amount of ink is lessened for ink tanks with a large volume. Consequently, the lower detection accuracy, leads to an uneconomical disposal of larger amounts of ink. Additionally, large volume ink tanks require a sensor device that can cover a greater detection range, which also results in more complicated configurations and higher manufacturing costs.
The present invention aims to solve the problems described above by providing an image forming apparatus that can detect the remaining amount of ink in each of a plurality of ink tanks with a simple configuration and high accuracy, such that the configuration of the image forming apparatus can be simplified and resulting in reduced manufacturing and maintenance costs.